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In this paper, a near-field coupled resonator antenna element is presented for power transfer applications. We propose an anchor shaped geometry that represents a combination of electric dipole and magnetic loop to realize stronger coupling over misaligned distances between the source and receiver antenna. The resonator was prototyped on textile substrate for wearable applications. A full-wave simulation of the power transfer efficiency is presented and compared with single-loop of the same size. The lateral misalignments are studied, and it is demonstrated that anchor-shaped resonators offer 80-90 % power transfer efficiency for misalignments as large as 70% of antenna lateral size. Simulation studies and measurement results are presented.

An Extremely Wideband (EWB) antenna array is presented that covers the entire UHF to C bands (0.13-7.63 GHz). The array has dual-linear polarization and is capable of wide-angle scanning. This array achieves an impressive 58:1 contiguous bandwidth at broadside and 42:1 bandwidth when scanning down to 60° in both E and H planes using a VSWR < 3 metric. In addition to building on the tightly coupled dipole array concept, the enabling novelty of this extremely wide bandwidth array is the use of a Frequency Selective Surface within the substrate that acts as a multistage narrowband notch filter to suppress periodic ground plane interference. Also, a highly improved impedance matching feed is employed. A 12×12 array prototype was fabricated and tested to verify the bandwidth and gain performance. The overall radiation efficiency was demonstrated to be 73% on average.

In this paper, a fully-flexible, low-cost and lightweight rectenna arrays suitable for wearable applications is presented. Textile-based antenna and rectifier were optimized to operate at 2.45 GHz. The latter exhibited an RF-to-DC conversion efficiency of 70 % at 8 dBm input power. Arrays of single elements resulting from the integration of antenna and rectifiers were implemented on shirts for power transfer applications. The measurement results demonstrate up to 600 μW of DC-power that was extracted from the array, allowing powering of low-power wearable electronics devices. A validation of the proof-of-concept was realized by lighting up three LEDs connected in parallel at distances of up to 60 cm from the source.

The shrinking spectrum availability has led to the development of creative approaches for spectrum allocation and reuse. A most promising approach for spectrum is the simultaneous transmit and receive (STAR) scheme. A major challenge in realizing STAR is the coupling of high power transmit (Tx) signals into the co-located receiver, leading to strong signal interference in the operating frequency. In addition, to this direct interference, cancellation of harmonics and the transmit noise is also necessary. Overall, for successful STAR realization, 3 signal components must be suppressed, namely 1)Tx signal, 2)Tx signal harmonics, and 3)Tx noise. In this paper, we present the design of RF cancellation of these components across 1 GHz using antenna and filters. In addition, we also show the effect of Tx noise coupling in an array environment and means to suppress it.

The congested sub-65GHz spectrum has steered the attention towards millimeter-wave (mm-wave) communication systems. To date, mm-wave systems have either sacrificed efficiency, bandwidth, or cost to be realized. In this paper, we present a low cost wideband feed for UWB Tightly Coupled Dipole Array (TCDA) operating across Ku-K-Ka bands and 5G bands (viz. 17.5-70 GHz) with emphasis on dual linear polarization. The presented array and feed are packaged in a compact profile (H = 2.7 mm) suitable for mobile and hand-held devices. Notably, the novelty of this antenna is the use of low-cost standard PCB processes, with Ball Grid Array (BGA) connection for a radiation efficient System in Package (SiP) approach. The presented mm-wave TCDA achieves over 52 GHz of instantaneous bandwidth for VSWR < 3 with scanning down to 60° in both E and H planes in infinite array simulations.

There is an emerging potential concerning textile electronics that combine the comfort, flexibility, and durability of textiles, with the functionality, connectivity, and intelligence of electronics. In this regard, the implementation of an ultra-wideband (UWB) antenna on textile will bring the advantages of a multi-functional system to a structure that will allow for a range of compressible/stretchable operations. In this paper, we present, for the first time, a low profile and low-cost UWB Tightly Coupled Dipole Array (TCDA) on a textile (i.e denim) substrate. A full-wave simulation of an infinite array, complete with textile and conductive thread characteristics, shows VSWR < 3 for scanning down to 60° from boresight in both E and H planes across a 6.5:1 bandwidth (0.9 GHz – 5.85 GHz). A near-theoretical realized gain value was also analyzed across the whole operating band.

Neural implants are used to continuously record essential signals in studies of neurological disorders. Existing systems involve the use of invasive procedures and revision surgeries to maintain adequate system performance. Our previous work demonstrated a fully-passive wireless system, tested in vitro, and was demonstrated capable of sensing even minute neural signals. This recorder has a minimum detectable signal (MDS) below 15 µV in amplitude and a RF sensitivity down to about - 135 dBm. While results have been promising, this system is yet to be used to study neurological disorders, the final intended application of the system. In this paper, for the first time, we evaluate the wireless neurosensing system's ability to capture the characteristic components of epilepsy, namely interictal epileptiform discharges. The present validation of this technology has great future clinical implications in neuroscience, especially epilepsy studies.

This paper presents performance analysis of compact on-body antennas over a female body phantom. These antennas are designed to operate in 2.4GHz industrial, scientific and medical (ISM) band. In the design process, full ground plane is used to minimize radiation towards the body as they are intended to operate in near-body scenarios for Wireless Body Area Networks (WBANs). They offer significant advantages of compactness, light weight, wide radiation pattern over the body surface to provide maximum coverage, and less sensitivity to the variation of the gap between the antenna and the human body. These advantages make them of high interest for on-body communications and wearable applications. Results show that these antennas have good performance and successfully communicate under various near-body scenarios.

In this paper, a textile-based novel antenna of anchor-shaped geometry is presented. The antenna was fabricated using automated embroidery of conductive thread referred to as Elektrisola-7 onto clothing substrate. Its power transfer efficiency (PTE) was measured and compared with existing textile-based resonators. The measurements suggest that the anchor-shaped antenna is more efficient than previously published on-textile antennas. It exhibited a power transfer efficiency of up to 83 % at 250 MHz and was used to collect up to 2 mW of DC power at proximity (~1 cm), The collected DC power is sufficient to continuously power an LED or LCD temperature sensor. The simplicity, lightweight, flexibility, and the ability to be unobtrusively integrated into garments make the design attractive to wearable technology applications.

We present measurement results for a novel ultrawideband (UWB) low-cost transmit/receive architecture with reduced power and hardware requirements that includes interference mitigation and accommodates multiple users. Specifically, hardware prototype is presented with measurements. To assess the systems performance and impact of the spreading/despreading process, a noise analysis conducted for the transmitter and receiver chains. Specifically, Bit-Error-Rate (BER) curves are generated from an Over-the-Air (OTA) communication link showing interference-to-signal ratios (gain margin) improved by at least 16 dB.

Recent advancements in differential Radio Frequency (RF) front-ends at millimeter-waves (mm-wave) create a need for high gain differentially fed arrays for 5G applications. In this paper, we present an ultra-wideband (UWB) mm-wave dual polarized Tightly Coupled Dipole Array (TCDA) with a novel differential feeding network. Notably, this differential TCDA (D-TCDA) is a low profile (thickness H = 1.85mm) and is developed for operation across K-Ka and 5G bands (viz. 26.4-79.4 GHz GHz) with low angle scanning. Full wave simulations show that the dual-polarized D-TCDA achieves 3.25:1 bandwidth with scanning to 45° at VSWR < 3 in both E and H planes in infinite array simulations.

The congested sub-6GHz spectrum has steered the attention towards millimeter-wave (mm-wave) communication systems. To date, mm-wave systems have either sacrificed efficiency, bandwidth, or cost to be realized. In this paper, we present a low-cost wideband feed for UWB Tightly Coupled Dipole Array (TCDA) operating across Ku-K-Ka bands and 5G bands (viz. 17.5-65 GHz) with emphasis on dual linear polarization. The presented array and feed are packaged in a compact profile (H = 2.7 mm) suitable for mobile and hand-held devices. Low-cost vertical to planar feed connections were investigated for a radiation efficient System in Package (SiP) approach. The presented mm-wave TCDA achieves over 52 GHz of instantaneous bandwidth for VSWR < 3 with scanning down to 60° in both E and H planes in infinite array simulations.

Recent studies focus on exploring the untouched millimeter-wave spectrum as it offers more bandwidth and higher data rates. Nevertheless, the high losses, power consumption, and cost of RF components at such frequencies remain prohibitive. In this paper, we present a novel compact beamforming concept using self-mixing techniques in an effort to downsize the overall number of RF components required and achieve higher efficiency. To do so, we introduce a novel analog beamforming method based on element-to-element mixing (BEEM) with flexibility in signal reception for any angle of arrival (AoA). Preliminary evaluation of the proposed BEEM topology is presented here. More specifically, we have conducted simulations with 16-quadrature amplitude modulation (16-QAM) to evaluate our beamforming concept. Simulations show that phase delay cancellation as well as coherent summation can be achieved using our BEEM topology, implying a near-theoretical diversity gain.

We present an $8.7\ \text{mm} \times 10\ \text{mm}$ fully passive brain implant, capable of wireless acquisition of neuropotentials down to $20\, \mu \text{V}_{\rm{pp}}$ , viz. three times lower than before. The implant receives a 2.4-GHz carrier signal from the external interrogator and mixes it with the neurosignals having a frequency of $f_{\rm{neuro}}$ . The mixing products ( $4.8\ \text{GHz}\,\pm \, f_{\rm{neuro}}$ ) are then transmitted back to the external interrogator and further demodulated to retrieve $f_{\rm{neuro}}$ . Previous work demonstrated a $15\ \text{mm} \times 16\ \text{mm}$ wireless and fully passive brain implant, capable of detecting emulated neuropotentials as low as $63\, \mu \text{V}_{\rm{pp}}$ . In this letter, we present a new neurosensing system with the following improved features: 1) 63% smaller implant; 2) 98% smaller interrogator antenna; 3) compliance with the strictest Federal Communications Commission standards for patient safety; 4) elimination of lumped components within the implant to preserve biocompatibility; and 5) three-times sensitivity improvement. This high sensitivity implies reading of most neural signals generated by the human brain.

Far-field characterization of array antennas can require many sequential measurements. In preparing such measurements, the necessary antenna repositioning and rotation can introduce small displacements. These displacements are not as important at low frequencies, but can be a significant fraction of a wavelength at the Ku-, Ka-, and millimeter-wave bands. Therefore, it is important to correct for them to obtain accurate array measurements. In this letter, we present a mathematical model describing the expected phase response of each antenna element for a given physical offset. This error model is applied to Ku-band measurements of an 8 $\times$ 8 dipole array. It is demonstrated that small movements of the antenna during measurement can be corrected via the proposed post-processing technique.

We present a novel load-bearing spiral antenna on conductive textile threads (E-threads) for conformal applications. The textile spiral exhibits a nearly 10:1 bandwidth (0.3–3 GHz) with circularly polarized gain of 6.5 dBi across the 1–3 GHz bandwidth. Such performance is unique for textiles and flexible surfaces. An important aspect of this letter is the demonstration of repeatable performance for this textile spiral antenna. Also, mechanical tests for the spiral showed no appreciable changes in performance, even after 300 flexing cycles. The spiral is a cavity-backed configuration with its ground plane also embroidered using very thin (diameter = 0.12 mm) Elektrisola E-threads. These threads can achieve geometrical precision down to 0.1 mm. To enhance robustness, high-strength Kevlar fabric was employed as the substrate. Overall, the proposed spiral is very attractive for several wideband, conformal, and load-bearing applications, such as airborne and wearables.

In this letter, we present a reflection-based phaseless method for circularly polarized (CP) gain characterization of antennas in the submillimeter-wave and terahertz bands. The broadside gain measurement using this method was demonstrated in the paper “Novel phaseless gain characterization for CP antennas at mm-wave and THz frequencies” ( IEEE Trans. Antennas Propag. , vol. 63, no. 10, pp. 4263–4270, Oct. 2015). Here, we extend the method to measure the main lobe of the antenna, which can be used for calculation of parameters such as beamwidth and Gaussicity. The method does not require phase consistency between orthogonal measurements and is, therefore, robust to misalignment errors. We present broadside gain and main-lobe pattern measurements in the WR-8 band to demonstrate the usefulness of the method.

We present a wideband tightly coupled dipole array (TCDA) with integrated balun and a novel superstrate consisting of printed frequency selective surface (FSS) for wide angle scanning. Although previous TCDAs have had decent scanning performance up to ±60°, use of dielectric superstrates are usually required, resulting in additional cost and fabrication complexity. In this paper, we replace the bulky dielectric layer(s) with periodic printed elements and yet achieve wide-angle and wideband impedance matching. The proposed approach provides superior performance of 6.1:1 bandwidth (0.5–3.1 GHz) with VSWR $E$ plane, ±70° in $D$ plane and ±60° in $H$ plane. The FSS, radiating dipoles and feed lines are designed and fabricated on the same vertically oriented printed circuit board, resulting in a low-cost and lightweight structure as compared to other low profile arrays. Measured scanning patterns of a $12 \times 12$ prototype are presented, showing good agreement with simulations.

A wideband high-isolation two-port antenna of low profile and omnidirectional pattern is presented. This two-port system consists of a collocated antenna pair with a cone antenna in the middle and a ring radiator around the cone, both placed over a rectangular ground plane. The overall dimensions are $0.64\lambda \times 0.64\lambda \times 0.11\lambda $ at the lowest frequency of operation. The isolation between the two ports is more than 37 dB and achieved by employing polarization orthogonality. The operational band is from 800 to 2700 MHz and the achieved isolation is verified with measurements of a fabricated prototype. Overall, the proposed antenna pair can be employed for simultaneous transmit and receive applications or MIMO and diversity systems in commercial wireless communication bands.

Curved ring-bar (CRB) slow-wave structure (SWS) has been presented before in order to design an SWS for high-power and wideband traveling-wave tube in S-band. It was analyzed using the coupled transmission line theory and predicted to deliver 1-MW output power across 1.8–2.4-GHz bandwidth. However, the slow-wave characteristics were not experimentally validated through measurements. In this paper, we present $\omega -\beta $ measurement results to experimentally demonstrate that the CRB structure is providing the predicted slow-wave characteristics at the S-band. A novel synthetic technique is used to determine the $\omega -\beta $ relation using a six-period fabricated CRB structure. The measurement results exhibit a phase velocity of $0.7c$ – $0.75c$ across 2–2.5 GHz with a maximum error of less than 5%. In addition, the measured on-axis interaction impedance was $>43\Omega $ across the specified frequencies implying satisfactory agreement with theoretical predictions.

In this paper, we present an efficient and direct method for computing the lower bound on $Q$ for arbitrary-shaped, perfectly conducting antenna geometries. We begin by deriving a new formula for $Q$ based on the currents induced on the antenna/scatterer and the method of moments (MoM) impedance matrix $[Z]$ . We then use this formula in conjunction with the theory of characteristic modes to find lower bounds on arbitrary-shaped electrically small antennas (ESAs). Current distributions that yield the minimum possible $Q$ are also given, providing for a powerful insight into the physical factors that affect $Q$ , and offer guidelines for improving the ESA designs constricted to arbitrary physical volumes. Several supporting examples are investigated, and appropriate comparisons to the literature are given to demonstrate the flexibility and effectiveness of our approach.

We report the design, fabrication, and measurements of reconfigurable terahertz (THz) filters using vanadium dioxide (VO2) phase-change material (PCM), which undergoes a transition between an insulator and metal phase at 68 °C (∼341 K). The filters are made of frequency selective surfaces (FSS) and heater are integrated for VO2 excitation. Two THz spatial filters are developed. A broadband on/off filter at 0.35 THz is demonstrated with 20 dB change in transmission between the on and off states. Then, a reconfigurable stopband FSS filter with tunable rejection from 0.75 to 0.55 THz is presented. The latter shows a peak with rejection of more than 90%. The two states of both filters are achieved at relatively low temperature of 68 °C, making them suitable for practical applications. Comparisons between simulation and measurement show excellent agreement for both 0.35 THz on/off filter and 0.75 to 0.55 THz tunable filters.

Previous work presented the concepts of mode dominance reversal using a novel slow wave structure (SWS). An example application of this mode reversal was a backward-wave oscillator operating in the $K_{a}$ band. However, the concepts have not yet been experimentally validated. In this paper, we use a scaled version of the SWS to experimentally demonstrate mode dominance reversal in the $S$ band. Using the detected resonances of the six SWS cells, a highly accurate synthetic technique is used to derive the dispersion curve. Simulations based on a commercial particle-in-cell code using this SWS design show peak output powers of 5.94 MW at 2.64 GHz with a 35% peak power electronic efficiency.

A coupled transmission line (TL)-based slow-wave structure is presented and characterized. This TL is a modified ring-loop structure referred to as curved ring bar. It inherits the features of the ring-loop structure, but includes elliptic loops to enhance the axial electric field for TM01 mode. The structure demonstrates wideband behavior and is especially designed for high-power traveling wave tube amplifiers. It is characterized using a pair of uniform and identical coupled TLs utilized to achieve desired dispersion characteristics. This characterization explains the dispersion curves and interaction impedance. A simple way to derive dispersion behavior in terms of circuit parameters is also provided. A traveling wave tube (TWT) model is also presented that gives an output power of 1 MW across 1.8–2.4 GHz. It is noted that the designed TWT provides a bandwidth of 20% and delivers an output power of 1 MW, larger than previously reported in S-band.

This special issue addresses various jammers and their effect on different processing stages and overall Global Navigation Satellite System (GNSS) receiver performance, and presents countermeasures and solutions to combat interference.

In this paper, we show how plasma-wave instability in an asymmetrically biased ungated InGaAs high-electron mobility transistor (HEMT) leads to terahertz emissions. Numerical calculations are provided using a new Maxwell-hydrodynamic solver. Using this solver, an accurate plasma-wave model is presented, accounting for nonuniform surroundings and finite dimensions of the 2D electron gas (2DEG) layer within the HEMT. We estimate that hundreds of nanowatts of power can be expected from such devices under ideal boundary conditions and sufficient channel mobility. Effects due to variations of carrier velocity, carrier concentration, and 2DEG confinement on the emitted power levels are also considered to provide design guidelines.

Future wireless communication systems will require much higher data rates. Suhc high rates require wideband arrays with beam forming capabilities. Concurrently, the RF spectrum will become more vulnerable due to intentional and unintentional interference. Therefore, interference cancellation and mitigation techniques as well as low cost wideband beamformers are required to ensure high gain secure communication for 5G commercial applications and for government needs.

In this chapter, we focus on these modern challenges faced by wideband array designers, and the substantial advancements which have been made over the past 5 years. Initially, we provide a review of UWB array designs to familiarize the reader with the two most common groups of UWB arrays. These are developed with an overview of their basic principles, practical design considerations, and illustrative examples from the literature. Thereafter, we delve into the particular challenges associated with designing these arrays for the emerging applications at millimeter-wave frequencies.

We present a novel ultra-wideband (UWB) low-cost transmit/receive architecture with reduced power and hardware requirements that includes interference mitigation capabilities and accommodates multiple users. Specifically, a novel encoding approach is introduced to multiplex signals across large bandwidths and achieve secure communication and interference mitigation through spread signals. In this paper, a detailed description of the proposed high data rate system architecture is presented. Simulations are also provided in presence of high power interferers with 8 concurrent users. To further assess the systems performance and impact of the encoding/decoding process, a noise analysis was conducted for the transmitter and receiver chains. Specifically, Bit Error Rate (BER) curves are generated at different stages of the system showing interference-to-signal ratios improvement by at least 10 dB.

We present a textile based RF-power harvester. This power harvester was designed to operate at 2.45 GHz to harvest Wi-Fi power for wearable electronic applications. The harvester comprises of: 1) 2.45 GHz patch antenna and 2) single-diode based rectifier circuits. The antenna and the circuit was implemented on organza and denim fabrics, respectively. The textile patch antenna demonstrated -10 dB Su-bandwidth from 2.38 GHz to 2.53 GHz with maximum realized gain of 4.7 dBi at broadside. Further, the textile-rectifier prototype demonstrated a 43% rectifying efficiency at 2.45 GHz with 0 dBm input power. Thus, a rectifier surface that occupies an area of only 2.2 cm×1.8 cm can operate small body-worn sensors.

A growing need for phased arrays in commercial markets has pushed for lower cost and much smaller arrays. Of particular interest is the delivery of high-data/high-throughput systems, including 5G connectivity. In this paper, we illustrate a design method to enable 75% lower cost aperture for a phased array, while maintaining electrical performance requirements. We are proposing a unique approach with a monolithic dielectric substrate for the aperture. Two feeding techniques are discussed for manufacturing ease and for direct integration with beamforming circuitry. Measurements for a proof-of-concept aperture are provided.

The loss-performance of conductive-textile microstrip lines (MLs) is investigated based on their embroidery patterns. We fabricated and tested MLs with different thread alignments and compared their performances with their PCB counterpart. In total, three textile MLs of different thread alignments (90°, 45° and 0° -fill stitches) were fabricated and measured. The MLs were embroidered onto denim fabric using a new class of conductive textile thread, referred to as Elektrisola-7, via an automated embroidery process. The measurements suggested that embroidery patterns (alignments of textile threads) can significantly affect the performance of the embroidered MLs. The textile ML fabricated with 90°-fill stitches exhibited minimum transmission loss, and achieved less than 0.3dB/cm-loss up to 3.5 GHz. This is the first time that different embroidery patterns are studied and reported. The results serve as a reference for future textile design fabrication.

We present a direction finding (DF) system using a Direct RF sampling technique. This technique promotes a low cost and versatile approach with minimum complexity. Specifically, a high-speed Digital-to-Analog Converter (DAC) as a transmitter and a high speed Analog-to-Digital Converter (ADC) as a receiver are used. The transmitted signal was a random Binary Phase Shift Keying (BPSK) Signal, coded with a Gold code of length 127. The total bandwidth is approximately 1.3 GHz.

A 2.4 GHz RF power transfer device is presented for wireless patient monitoring in the radiated near-field zone. Instead of near-field coils that are highly sensitive to misalignments and distance, an external button-sized rectifying antenna (rectenna) is proposed. This rectenna can be easily attached to the patient's skin or clothing. It consists of a small (15 × 25 mm2) antenna connected to a voltage doubling rectifier with a minimum conversion loss of 4.2 dB. A position sensitivity analysis is demonstrated across a 20 cm diameter, and concludes with a demonstration of a temperature sensor being activated wirelessly on a human phantom.

We demonstrate a wideband scanning 4-arm spiral antenna array with high transmit/receive isolation for Simultaneous Transmit and Receive (STAR). STAR increases a channel's spectral efficiency by transmitting and receiving across the full bandwidth of a channel. To our knowledge, this is the first STAR array to demonstrate scanning across GHz bandwidths. Each 4-arm spiral element is divided into two arms for transmit and two more for receive. To suppress grating lobes, the element spacing is kept at less than λ/2. A 3×3 array prototype was fabricated and measurements agree well with simulations.

Differential RF front-end components provide greater immunity to ground noise and distortion by suppressing external interference. Recent advancements in differential RF front-end components offer high dynamic range, high input linearity, and low noise in the transceiver chain. However, differential phased arrays are not inherently ultra-wideband (UWB). To create a wideband differentially fed array for chip-integrated transceivers, a novel approach was taken on the well-established UWB Tightly Coupled Dipole Array (TCDA). This differential TCDA (D-TCDA) is proposed for S-Ku band (3–18 GHz) communications with emphasis on dual linear polarization and wide-angle scanning. The array achieves 6:1 bandwidth for VSWR < 3 at broadside with scanning down to 45° from boresight in both E and H planes. The array exhibits very low cross-polarization, on the order of 70 dB.

In this paper a new designed thin wide band antenna is introduced. The proposed monopole antenna which was fabricated on flexible substrate has compact geometry area of 51 ⨯ 22 mm2 that makes it suitable for handheld applications. The antenna was featured with three rectangular slabs at the bottom layer in order to improve boresight gain performance over spectrum of operation. Moreover., the antenna produces semi omni directive radiation and has radiation efficiency more than 90 % over its bandwidth of operation. The antenna design along with simulation and experimental results are presented in this work.

A passive, wireless and batteryless multi-channel (8 channels) brain implant is proposed with the following unique features: a) 28 times better sensitivity, b) 2 times smaller footprint, and c) scalability to 100s or even 1000s of channels. To verify the operation within biological tissues, in-vitro measurements are presented using fresh pig skin. Experimental results show that the proposed neuro-sensing system exhibits 20 μ V pp sensivity at all channels. That is, it can record any signal generated by the human brain. Overall, this technology brings forward transformational opportunities for patients with epilepsy, Alzheimer's and Parkinson's disease.

To address the challenges of the ever increasing spectrum demands, one approach is to implement in-band full duplex wireless systems. A popular approach for implementing full duplex communication without increasing resource utilization is the simultaneous transmit and receive (STAR) scheme. However, coupling of the high power transmit signals onto the colocated receiver leads to high signal interference in the operating frequency. Suppressing the high power self-interference is necessary for a successful STAR transceiver implementation, but is very challenging. In this paper, we present the design and implementation of RF self-interference cancellation filters, by suppressing the coupled signal 25dB across 1GHz bandwidth. This wideband cancellation should be contrasted to past cancellation that were narrowband and did not exceed ~100MHz bandwidth.

We introduce a new method to significantly reduce the size and thickness of waveguides using a new class of coupled transmission lines (CTLs). By increasing CTLs into the waveguide, new modes are generated that lower the cutoff frequency, and therefore reducing size for the same operational frequency. We considered circular as well rectangular waveguides. Due to their cutoff frequency CTL-loaded waveguides can be used at much lower frequencies and realized as extremely thin or sheet like transmission lines.

To address the need for continuous and localized brain electrical activity recordings, implantable neurosensing systems are often used. However, current systems involve highly-invasive procedures that can interrupt day-to-day activities. This paper presents an approach for developing a device that can be used to obtain neural data during normal activity and without hindering the quality of life. In this paper, for the first time, we present the design and application of improved neural probes for a fully-passive wireless brain implant. The integration of these neural probes to the neurosensing system results in enhanced impedance matching capable of sensing neural signals as low as 15 μVpp and improve the RF sensitivity to ~ −135 dBm. As such, all neural activity can be recorded.

To address the need for high-quality brain monitoring, implantable systems are often used. However, these systems require significantly invasive procedures. This paper presents the development of probes specific to a device that can be used to record neural data during normal day-to-day activity. Here, the design of low-impedance neural probes for a fully-passive wireless brain implant is introduced and employed in a series of in vitro experiments. The integration of these neural probes to the neurosensing system results in enhanced impedance matching. As a result, neural signals as low as 15 µVpp can be detected with an RF sensitivity of ~ −135 dBm. This implies that the neurosensing system can record all neural activity measurable at the cortical surface.

TPID5180187. Conductive fibers are used to construct the metallic parts on a PDMS composite. To characterize the performance, two identical antennas are designed, one using the PDMS composite while the other on conventional dielectric materials. The antenna exhibits a matched bandwidth of 59.9%, ranging from 3.43 to 11.1 GHz. With excellent performance and high flexibility, this antenna is well-suited for body area networks and other wearable applications.

In this paper, we present for the first time a novel dual-linear polarized phase array based on tightly coupled dipole topology. The array operates across an impressive 9:1 impedance bandwidth spanning 2–18GHz with scanning capability down to 60o from boresight. Importantly, the array is extremely low profile, with a total height less than 12mm (λ low /10). The overall geometry consists of cross-located tightly coupled dipoles integrated with a folded Marchand balun that serves as an impedance transformer and a feeding network. The traditional dielectric superstrate is replaced with double layers of frequency selective surfaces (FSS) to enable scanning down to 60o in both E and H plan across the entire band. Notably, the polarization and port-to-port isolations are kept at least 40dB at broadside and 30dB with scanning cases. Such high isolation makes this array great candidate for Simultaneous Transmit and Receive (STAR) systems.

We present a low profile wideband spiral antenna array with high transmit/receive (Tx/Rx) isolation and beam steering capability for simultaneous transmit and receive (STAR) systems. STAR increases a channel's spectral efficiency by transmitting and receiving across the full bandwidth of a channel. To our knowledge, this is the first wideband STAR spiral array with scanning. Each 4-arm spiral element consists of two arms for Tx and two more for Rx. To suppress grating lobes, the element spacing is kept at λ HIGH /2. Full wave infinite array simulations show the port-to-port Tx/Rx isolation is >40dB at boresight across a 3 GHz bandwidth from 2–5GHz (2.5:1). This level of port-to-port isolation reduces to about 30dB when scanning down to 30°. In addition, VSWR is < 2 and axial ratio < 3dB. A 3×3 array was fabricated and showed an average Tx/Rx isolation of 36dB with VSWR < 2.4.

Lightweight wireless implantable insulin pumps are highly desired by Type 1 Diabetes patients. This study reports the development of a polypyrrole-electroactuated micropump equipped with a non-fouling catheter tip. It can generate a consistent volumetric output of 16 μL at an RF power of 1.2 mW, supplied by an integrated wireless harvester. This motor-and-battery-free design significantly improves the pump's adoptability and biocompatibility.

In this work, we develop a class of broadband circularly polarized (CP) horn antennas that are realizable at sub-mm-wave and terahertz frequencies. Here, the underlying technology is a hexagonal waveguide that act as linear to circular polarizer enabling the generation circularly polarized (CP) wave in a waveguide environment. We have developed analytical models to characterize these waveguides and thus optimize the designs of CP horns. The optimized designs have shown 3dB axial-ratio bandwidths upto 30–40% with 18–21 dBi gain in WR-8 band.

A dual-polarized, tightly coupled dipole array (TCDA), delivering 13.1:1 bandwidth, is presented. The array incorporates a resistive sheet (R-Card) in the substrate to suppress resonances within the operational band and employs a dielectric layer as a superstrate to maintain high efficiency. The simulated infinite array demonstrates broadside VSWR -2.2 is dB across all frequencies and scanning angles. An 8×8 prototype was fabricated and tested to validate the design. Measured array gain and mid-band and high-frequency patterns for the two principal scanning planes are presented, demonstrating good agreement with the respective simulations.